The Hematopathology Fellowship has been highly successful in attracting outstanding applicants and in providing them with training in hematopathology, emphasizing outstanding clinical diagnosis, and specialized diagnostic tools including molecular diagnostics and flow cytometry. The fellowship has been ACGME accredited since 2000 and graduating fellows have had a nearly a 100% first time pass rate on the accrediting examination given by the American Board of Pathology. Graduating fellows have gone on to establish independent careers in academic medicine, including appointments in recent years at Duke University, Northwestern University Medical Center, Moffit Cancer Center, Children's National Medical Center, University of Chicago, Weill Cornell Medical School), City of Hope National Medical Center, The Mayo Clinic, Memorial Sloan Kettering Cancer Center, Henry Ford Hospital, University of California -San Francisco Medical Center, Ohio State Medical Center, and the Cleveland Clinic. Four recent graduates have successfully competed for independent NIH RO1 funding. Fellows are encouraged to participate in clinical research; representative publications by trainees over the past year include publications on Hodgkin lymphoma, HHV6-related lymphoid proliferations, histiocytic and dendritic cell neoplasms, EBV-related B-cell lymphomas. and Castleman disease. In one representative project, we identified a new form of marginal zone lymphoma that is EBV-positive. Traditionally low-grade B-cell lymphomas have been excluded from the category of monomorphic posttransplant lymphoproliferative disorders. However, recent reports identified Epstein-Barr virus-positive (EBV) extranodal marginal zone lymphomas (MZL), almost exclusively seen in the posttransplant setting. Some reported cases responded to reduced immunosuppression, suggesting that they should be considered as a form of posttransplant lymphoproliferative disorders. We identified 10 cases of EBV MZL, 9 in extranodal sites and 1 presenting in lymph node. Two cases arose following solid organ transplantation, but other settings included iatrogenic immunosuppression for rheumatoid arthritis (2); prior chemotherapy (2); congenital immune deficiency (1); and increased age (3), as the only potential cause of immune dysfunction. There were 4 males and 6 females; age range 18 to 86. The atypical plasmacytoid and/or monocytoid B cells were positive for EBV in all cases, with either latency I or II in all cases tested. Monotypic light chain expression was shown in all with 6 cases positive for IgG, and 2 for IgM, undetermined in 2. Clonal immunoglobulin gene rearrangement was positive in all cases with successful amplification. MYD88 L265P was wild type in the 6 cases tested. We show that EBV marginal zone lymphomas can arise in a variety of clinical settings, and are most often extranodal. Treatment varied, but most patients had clinically indolent disease with response to reduction of immune suppression, or immunochemotherapy. This study shows that close connection between EBV-positive lymphomas arising in diverse immunodeficiency settings. It also calls attention to the need for studies of EBV in cases of marginal zone lymphoma, in which a role for EBV may not be suspected. We report new data regarding ALK-positive histiocytosis, and conclude that this lesion should be recognized as a separate disease that is highly associated with the KIF5B-ALK fusion, and may be seen in both children and adults.